The present invention relates an to exercising apparatus, and, more particularly, to such apparatus intended primarily, though not exclusively, for exercising the abdominal muscles of person.
The abdominal area of the human body is comprised of four muscle groups including the rectus abdominis, the external obliques, the internal obliques and the transverse abdominis.
The rectus abdominis muscles are a pair of long flat muscles located on either side of the navel which run the length of the abdominal area, from the pubic bone to the chest. The rectus abdominis originates in the crest of the pubis and inserts at the cartilage of the fifth, sixth, and seventh ribs, and the sternum. They are interconnected by the linea alba, a band of fibrous connective tissue. The rectus abdominis pulls the torso toward the hips and is responsible for tilting the pelvis which effects the curvature of the lower back.
The external obliques are broad, thin, flat muscles situated on the lateral and anterior parts of the abdomen and attached by fibrous connective tissue to the abdominis rectus. They originate from the lower eight ribs and attach with the serratus muscle that covers the ribs. The external obliques aid in the twisting of the trunk. Specifically, the left external oblique is used when twisting to the right, and the right external oblique is used when twisting to the left.
The internal obliques are thin, small muscles which lie underneath the external obliques and run in a diagonally opposite direction. They extend from the lateral margins of the lower rib cage and are directed inwardly toward the rim of the pelvic iliac bone. The internal obliques are also attached to the abdominis rectus muscles by fibrous connective tissue. The internal oblique muscles aid the trunk in twisting in the same direction as the side they are on. Specifically, the left internal oblique aids the right external oblique to twist the torso to the left, while the right internal oblique aids the left external oblique to twist the torso to the right.
The transverse abdominis is a broad, very thin muscle which runs horizontally across the abdominal wall and along the midsection underneath the external and internal obliques. The transverse abdominis originates from the rim of the crest of the ilium, the lower six ribs, running along the outer part of the inguinal ligament, and connects to the lumbar muscle. It pulls the abdominal wall inward, forcing expiration.
Because these four muscles are located in the center of the body, the process of isolating and developing them has proven to be a difficult and often rigorous task.
One popular exercise for the abdominal muscles is known as the "sit-up." During such an exercise, a person lying in a supine position with knees flexed into an upward position and hands behind the neck, slowly curls and uncurls the upper body so as to bring the head toward the stationary knees. Typically, the purpose of these types of abdominal flexion exercises is to require the upper torso to flex in a curling and uncurling manner so as to bring about a strengthening of the muscles of the abdomen, particularly the rectus abdominis.
Variations of the sit-up exercise include starting from a fully flexed position and lowering to an intermediate position which is held before returning to the upright position. Another variation, called a "sit-up twist," entails a twisting motion at the end of the upward movement such that one elbow touches the opposite knee. A twisting motion at the end of the curl, such as in a sit-up twist, serves to exercise the external obliques in addition to the rectus abdominis.
Occasionally, the sit-up is performed with the aid of a partner commonly referred to as a "spotter." The role of the spotter is to hold down the feet of the exerciser so as to restrict movement of the legs during the sit-up. Alternatively, a "sit-up board" may be used. The sit-up board includes an inclined, cushioned surface that functions as a seat, and some type of anchor, such as a strap or padded bar, under which the ankles are secured. A separate knee support for supporting the backs of the knees also is found in many sit-up boards. The only way to adjust the resistance while performing a traditional sit-up regardless of whether performed alone, with a spotter, or on a sit-up board, is for the user to grasp a weight plate or other heavy substance across his chest to increase the effort required to raise the upper torso to the upright position.
Another prevalent, but somewhat more strenuous exercise for the abdominal muscles is referred to as the "leg lift." The most basic type of leg lift entails a person lying supine to extend and raise both legs upward to approximately 90 degrees and then to lower them to their original position. Variations on the leg lift include bending at the knees, alternating leg lifts, raising the legs to different heights and in different directions, and simulating a bicycle pedaling motion in the air. Typically, leg lift exercises develop the transverse abdominis and lower rectus abdominis muscles as portions of the lower body are raised and lowered while the upper body remains stationary.
In recent years, the growth of the field of sports medicine has brought with it much criticism of the sit-up and other conventional abdominal exercises. The first wave of criticism revolved around the positioning of the hands and arms while performing the sit-up. These critics claimed that positioning the hands clasped behind the neck put undue stress on the neck and spine when doing a sit-up. Therefore, to avoid injury to the neck and spine, several alternatives were recommended, including positioning the hands on ears, hands on top of head, hands folded across chest, and hands extended forward. Significantly, a consensus evolved that performing a sit-up with the hands and arms extended fully forward is the position of least resistance and least stress upon the neck.
The second attack on the sit-up relied on the theory that the flexion of the lumbar and thoracic spine over a significant range of motion might cause strain on the lower back. Accordingly, some in the medical field advocated limiting the range of motion of the spine during abdominal exercises to prevent injury to the lower back and spine. The result of their efforts was a widespread adoption and use of a variation on the sit-up referred to as a "crunch."
A "crunch" is performed when a person lying on his back with knees bent and hands folded behind his head raises only his shoulder blades off the floor in a forward-curling motion and then lowers his shoulders to the starting position. During the forward-curling motion, the small of the back remains in contact with the floor resulting in an exercise with a very limited range of motion. This exercise succeeds in isolating and developing the upper rectus abdominis, but leaves the remaining muscles of the abdomen unaffected.
In response to the criticism against the traditional sit-up exercise, many new machines were developed beginning in the early 1990's touting less strenuous means of exercising the abdominal muscles. The most popular of these machines suffer three major drawbacks, that is, 1) they are not cardiovascular fitness devices and will not "spot reduce" fat; 2) they have no or very limited resistance control mechanisms; and 3) they activate only a very small portion of the four muscle groups of the abdomen.
In response to these type of machines, many in the sports health industry have returned to advocating traditional abdominal exercises capable of being performed on a simple exercise mat laid on the floor.